matiaozhi.m

线形调频信号带码调制,程序是自己写的 仿真效果也不错 环境是MATLAB

code=[1,1,1,0,1,0,1];
tao=20e-6;
fc=0.5e6;
fs=40000000;ts=1/fs;
B=10000000;
t_tao=0:1/fs:tao-1/fs; % 码内采样点数
k=B/fs*2*pi/max(t_tao);
n=length(code);%码长
N=length(t_tao);
pha=0;
kk=cumsum(t_tao);
s=zeros(1,n*N);sss=zeros(1,n*N);
for i=1:n
    if code(i)==1
                pha=pi;
            else pha=0;
            end
           s(1,(i-1)*N+1:i*N)=j*sin(2*pi*fc*t_tao+k*cumsum(t_tao))+cos(2*pi*fc*t_tao+k*cumsum(t_tao));
           sss=s.*conj(s);
    end
% t=0:1/fs:7*tao-1/fs;
% ss=cos(2*pi*fc*t_tao+k*cumsum(t_tao));
subplot(211);
plot(real(s));xlabel('t(s)'),
title('混合调治信号（7位码+线形调频信号）');
s_fft=abs(fft(s(1:(N*n))));
s_fft=abs(fft(s));
subplot(212);
plot((0:fs/(N*n):fs/2-fs/(N*n)),abs(s_fft(1:(N*n)/2)));xlabel('HZ'),title('信号频谱');

w=64;%加窗
l=w/2;
tn=(N*n-w)/l+1;
nfft=512;
%TF=zeros(tn,nfft);
for i=1:tn
    xw=s((i-1)*32+1:i*32+32);
    temp=fft(xw,nfft);
    temp=fftshift(temp);
    TF(i,:)=temp;
end
fnew=((1:nfft)-nfft/2)*fs/nfft;
tnew=(1:tn)*l*(1/fs);
[F,T]=meshgrid(fnew,tnew);
mesh(F,T,abs(TF));
figure(5);
contour(F,T,abs(TF));grid;